Process for the production of valuable organic and inorganic substances from waste sulfite liquor



PATENT OF.FICE.

UNITED STATES.

aonnnr WILHELM srannnmma'r,

PRODUCTION OF VALUABLE ORGANIC AND INORGANIC STANCES FRQM WASTE SULIEI'IE LIQUOR.

PROCESS FOR THE No Drawing.

Valuable Or anic and Inorganic Substances from Waste ulfite Liquor; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it iqppertains to make and use the same. the waste liquors of sulfite cellulose factories for "thepurpose of separating the or ganic and inorganic constituents of the same.

A process forthis, purposehas been described in my United States Patent No. 1,149,420, according to which the sulfurous acid content of the liquor is transformed into sulfuric acid, whereby the. calcium-lignosulfite is decomposed and precipitated, the

process being carried out under high pressure and high temperature, preferably by introducing air into the reaction vessel in order to raise the pressure and to secure oxidation.

It is a fact, however, that the sulfite process is now carried out in several ways, so that the waste liquor is of'varying composition or quality, and often contains a very small quantity offree sulfurous acid. It is then diificult to obtain the necessary quantity of sulfuric acidfor starting the reaction above mentioned. Sometimes the liquor is also first used for the production of alcohol, and in such cases there will be no free sulfurous acid at all in the liquor. It is then necessaryto add a small quantity of sulfuric acid, for instance 01.0.5% for starting the process.

My present invention relates to a special manner of obtaining this addition of sulfuric acid. According to my invention the addition of the sulfuric acid to the waste liquor is accomplished by'the formation of the acid in the reaction vessel. The acid is formed therein b introducing gases or vapors containing 0 into the vessel in such manner that the necessary pressure is maintained. These gases or vapors of acid character are for instance the gases in at the moment when it is to be blown ofl:' for lowering the pressure. In the preferred way of carrying out my invention I introduce such gases into the autoclave used for de- Specification of Letters Patent.

invention relates to the treatment of into Sulfuric acid and free Sulfun .tion in the'liquor in the usualmanner. 4

The transforming of- SO to sulfuric iana sulfite digester or eorrnn'none, SWEDEN.

SUB-

Patented Dec. 7,1520.

Application filed May" 19, 19'17.".S-,eri a1 No. 167,838.

composition of-the waste liquor under'a pressure correspondlng to about one atmosphere above normal pressure. The liquor is thereafter raised to thenecessary temperature in any suitable manner, whereupon :the gas in-- troduced wlll expand and raise the pressure in the autoclave above the steam pressure "whichwould' prevail at the same temperature. Whenthe liquor has'reached the necessary temperature, usually about 190 to 200 centigrade', the sulfurous 'acid present will instantly 'The sulfuric' acid thus formed completes the reachydrid just mentioned according to the equation: 1

. gso zaso qgs is known for instance from Gartner and Berthelots publications and has also been studied by Professor P. Klason in connection with the experiments relating to.the properties of the 'sulfite liquor. Thisreaction seems,

however, to have been studied only at lower temperatures (between 135140 centigrade). To transform sulfurous acid to sulfuric acid according to the above equation at these temperatures would require from,

eight to ten hours. On such basis it would be impracticable to carry out the process on an industrial scale as the cost would be excessive. I have discovered that by employing a relatively high temperature preferably be transformed by self-oxidation gases, not only the sulfurous acid is operative in the decomposition of the calcium-lignosulfite, but that also such acids as formic acid, acetic acid and other acid organic compounds present in the gases take active part in the process. mixed with sulfurous acid, only small quantities of the latter acid is necessary to make the waste liquor rich enough in acid to secure decomposition. 1

It is evident that instead ofgases obtained from the cellulose-process, gases or vapors produced in other. rocesses but containing these compounds 0 acid character may be used for carrying out the process.

If such acids are present When carrying out the present invention, the process as a whole may'be performed :substantially in the same way as described lignosulfite compounds.

When the process is carried out in a-continuous Way, there being used a number of autoclaves, the quantity of sulfurous acid necessary can be reduced by transferring the liberated S0 from one autoclave to another. Furthermore, if the colloidal sulfur which is liberated by the'decomposition is sublimed with the gases and exposed to an increase in temperature of 50?" centigrade in the presence of air, it willburn and form an equivalent quantity of sulfurous acid.-

The air necessary for this purpose may be introduced into the autoclave where it is mixed with the S0 and the vaporized sulfur and afterward causes the oxidation of the sulfur, when the gas is being heated as men- "tioned. The small quantities of calcium and sodium sulfites present in the liquor are converted to sulfates and sulfids. The sulfids are further acted upon by the sulfuric acid formed during the process and hydrogen sulfid is liberated. The latter reacts with the S0 to form colloidal sulfur.

As will be understood from the above description it is necessary to add S0 only upon starting the first autoclave as during the decomposition of the liquor more or less S0 is formed, which is then utilized for the next autoclave. Furthermore, considerable quantitiesof SO may be recovered in this way and utilized in the sulfite process.

If it is desired to obtain a still stronger acid mixture, thereby. intensifying the action, this may be brought about by adding to the gases obtained from the digesters a suitable oxidizing agent such as atmospheric oxy en.

e foregoing detailed description has been given for clearness of understanding and no undue limitation shouldbe deduced therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a process for the production of valuable organic and inorganic-substances from waste llquor from the sulfite cellulose process, the step which consists in introducing Into an autoclave, containing-the said-waste llquor, gases or vapors of an acid character Y in a'quantity sufiicient to create a pressure which is considerably higher than the steam pressure corresponding to the temperature into an autoclave, containing the said waste liquor, waste gases or vapors from a sulfite cellulose digest'er in a quantity sufficient to create a pressure which is conslderably 'higher'than' the steam pressure correspond ing to the temperature in the autoclave, sald temperature and pressure being sufiicient to cause the self-oxidation of 'sulfurous acid.

3. The process for the production of valuable organic and inorganic substances from waste liquor from the sulfite cellulose process, which comprises introducing gases or' vapors of an acid character into an autoclave containing the said waste liquor, increasing the temperature and pressure whereby the S0 present in the autoclave is converted into sulfuric acid and free sulfur and decomposition of the liquor is effected, transferring thereafter gas containing free sulfur from the autoclave to a container where it is heated in the resence of air to oxidize the free sulfur to O and utilizing the said gas for the decomposition of another charge of waste liquor.-

4. The'process for the production of valuable organic and inorganic substances from waste liquor from the sulfite cellulose process', which comprises, introducing' gases or vapors of-an acid character and an oxidizing agent under pressureinto an autoclave containing the waste liquor, increasing the temperature and pressure whereby the S0 present is transformed into sulfuric acid and free sulfur, thereby causing decomposition of the liquor, transferring the said S0 and free sulfur to a container where it is heated in the presence of air, so as to cause an oxidation of the free sulfur to $0 and utilizing the said SO for the decomposition of another charge of liquor.

5. The process for the production of valuable organic and inorganic substances from waste liquor from the sulfite cellulose process, which comprises introducing gases or vapors of an acid character together with air under pressure into an autoclave containing the waste liquor, increasing the temperature and pressure whereby the S0 present is transformed into sulfuric acid and-free sulfur, thereby causing decomposition of the liquor, transferring the S0 thus liberated and the free sulfur to a container where they are heated in the presence of air, so as to cause an oxidation of the free sulfur to S0,, andutilizing the said S0, for the decomposition of another charge of liquor.

6. The process for the recovery of valuwaste liquor from the sulfite cellulose process, which comprises introducing a gas containing S0 .into an autoclave containing said waste liquor, raising the temperature and pressure until a part of the resultant sulfurous acid is decomposed forming sulfnr and sulfuric acid, said sulfuric acid reacting upon and decomposing the waste liquor thereby precipitating the organic constituents and calcium sulfate, separating the precipitate from the liquid, and leading the gas fromthe said autoclave to another autoclave for decompositign of waste liquor.

7 The process'for therecovery of valuable. organic and inorganic substances from waste liquor from the sulfite cellulose process, which comprises introducing a gas containing SO into an autoclave containing said waste liquor, raising the temperature and pressure until a part of the resultant sulfurous acid is decomposed forming sulfur and sulfuric acid, said sulfuric acid reacting upon and decomposing the waste liquor thereby precipitating the organicconstituents and calcium sulfate, separating the precipitate from the liquid, leading the ga' containing sulfur dioxid and sulfur from the said autoclave to a container, mixing it with a gas comprising oxygen, raising the temperature of the mixture until the sulfur is oxidized to S0,, and leading the gas to another autoclave for decomposition of waste liquor.

8. The process, which comprises subjecting waste sulfite liquor to the action of an acid gas at a temperature and pressure sufficient to cause the rapid self-oxidation of the S0 liberated from said liquor.

9. The process which comprises subjecting waste sulfite liquor containing but little or no free sulfurous acid, which comprises subjecting the liquor to the action of acid gases containing SO at a temperature and pressure sufficient to cause the rapid self-oxidation ofthe resultant sulfurous acid.

10. The process, which comprises subject thereafter changing the temperature conditions to cause the oxidation of the sulfur to sulfur dioxid.

1.2. The process, which comprises subject ing waste sulfite liquor to the action of an acid gas at a temperature of about 190200 (3., and a pressure ofabout 2O atmospheres.

13. The process which comprises subjecting waste sulfite liquor to the action of SO at a temperature of about 190 to 200 C. and a pressure of about 20 atmospheres.

' ROBERT WILHELM STREHLENERT.

Witness:

' C. DORMAN. 

